Solventless wire enamels are desirable from the standpoint of protection of the environment and the saving of energy required for curing. However, solventless wire enamels which are cured with heat alone can volatilize a high percentage of the monomer. This occurs even when highly non-volatile monomers such as trimethylolpropane triacrylate and tetraethylene glycol diacrylate are used due to the very high temperatures required for the very fast cure times effected in a normal wire enamel coating operation. In an ultraviolet (UV) curing operation on the other hand, the monomers are polymerized very rapidly without excessive heating and little or no monomer is volatilized.
Acrylic monomer formulations have been made which can be cured readily with ultraviolet radiation, but these have shown definite shortcomings when used as wire enamels. Also, acrylated epoxies, urethanes, and polyesters have been adapted to UV curing with similar shortcomings, particularly a poor combination of thermoplastic flow and heat shock resistance.